Construction machines such as a large-size hydraulic excavator which operates in a mine or the like, and other working machines, are often required to continuously operate 24 hours per day and 365 days per year with almost no stopping. In such a case, before a machine is abnormally stopped, it is necessary to keep devices in perfect conditions by subjecting them to maintenance work beforehand. In general, a specialized maintenance person periodically performs inspection based on inspection work to check whether or not an abnormal state has occurred in any of the devices. If an abnormal state is detected, required maintenance work is performed to maintain the device in a good condition.
On the other hand, the devices need to be stopped for inspection and maintenance work. Therefore, for an operation manager who wants to continuously operate the devices, the inspection and maintenance work will often be troublesome for operation while the devices operates normally.
In recent years, as is the case with a flight recorder of an airplane, a recorder is sometimes provided (a drive recorder; refer to patent document 1) on the main body of devices so that the recorder is made full use of in various ways. Various kinds of sensors are provided for the devices. Accordingly, inspection work to check whether or not maintenance work is required can be achieved by checking internal state information about the devices, which is output by the sensors. Heretofore, alarm information is usually output by a diagnostic circuit inside a device. However, at the moment when such alarm information is issued, a device state may have already become worse and, in the worst case, the operation of the device may stop. However, when an inspection is made by use of sensor information recorded in a recorder, the state that the device has failed can be known before the operation of the device stops. This makes it possible to make a maintenance plan. Recently, a diagnostic apparatus in which various kinds of sensor information recorded by a recorder is subjected to data processing by a computer is achieving widespread use.
As a processing method for processing the time series data, there are methods described in patent documents 2, 3. According to the method described in the patent document 2, a state which differs from a normal state is detected for the purpose of detecting illegal entrance into a computer network. According to the method described in the patent document 3, whether or not a movable body is in a moving state or in a stationary state is detected from a state of a radio wave at a communications terminal of the movable body.
In addition, patent document 4 proposes a technique in which diagnosis of a device is learned so as to make use of the learned diagnosis for the detection of an abnormal state.
Moreover, for example, patent documents 5, 6 describe a fault diagnostic apparatus of a working machine such as a hydraulic excavator. According to the patent document 5, the fault diagnosis includes the steps of: detecting, by each sensor, the state quantity relating to an operating state of an engine cooling water system of a hydraulic excavator; recording, as state quantity data, the state quantity detected by each sensor; comparing the recorded state quantity data with a specified reference value range corresponding to the state quantity data; and if the state quantity data is not within the reference value range, judging the state quantity data to be an abnormal state. According to the patent document 6, the processing includes the steps of: recording information, which are detected by each sensor for detecting the state quantity relating to an operating state of an intake and exhaust system of an engine, in a data recording device as input operation data, the information including intercooler inlet pressure, intercooler outlet pressure, an intercooler inlet temperature, intercooler outlet temperature, exhaust gas temperature of the engine, outdoor air temperature, engine speed, and a throttle position; recording, in the data recording device, comparison data to be compared with operation data; inputting the operation data and the comparison data, which have been recorded in the data recording device, into a display controller; and outputting the operation data and the comparison data on a display unit as display signals.    Patent document 1: JP, A 2002-73153    Patent document 2: JP, A 2005-4658    Patent document 3: JP, A 2002-217811    Patent document 4: JP, A 2003-516275    Patent document 5: JP, A 2005-180225    Patent document 6: JP, A 2005-163754